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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef widget_windows_WinWindowOcclusionTracker_h
#define widget_windows_WinWindowOcclusionTracker_h
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include "nsIWeakReferenceUtils.h"
#include "mozilla/ThreadSafeWeakPtr.h"
#include "mozilla/widget/WindowOcclusionState.h"
#include "mozilla/widget/WinEventObserver.h"
class nsBaseWidget;
struct IVirtualDesktopManager;
class WinWindowOcclusionTrackerTest;
class WinWindowOcclusionTrackerInteractiveTest;
namespace base {
class Thread;
} // namespace base
namespace mozilla {
namespace layers {
class SynchronousTask;
namespace widget {
class OcclusionUpdateRunnable;
class SerializedTaskDispatcher;
class UpdateOcclusionStateRunnable;
// This class handles window occlusion tracking by using HWND.
// Implementation is borrowed from chromium's NativeWindowOcclusionTrackerWin.
class WinWindowOcclusionTracker final : public DisplayStatusListener,
public SessionChangeListener {
/// Can only be called from the main thread.
static WinWindowOcclusionTracker* Get();
/// Can only be called from the main thread.
static void Ensure();
/// Can only be called from the main thread.
static void ShutDown();
/// Can be called from any thread.
static MessageLoop* OcclusionCalculatorLoop();
/// Can be called from any thread.
static bool IsInWinWindowOcclusionThread();
/// Can only be called from the main thread.
void EnsureDisplayStatusObserver();
/// Can only be called from the main thread.
void EnsureSessionChangeObserver();
// Enables notifying to widget via NotifyOcclusionState() when the occlusion
// state has been computed.
void Enable(nsBaseWidget* aWindow, HWND aHwnd);
// Disables notifying to widget via NotifyOcclusionState() when the occlusion
// state has been computed.
void Disable(nsBaseWidget* aWindow, HWND aHwnd);
// Called when widget's visibility is changed
void OnWindowVisibilityChanged(nsBaseWidget* aWindow, bool aVisible);
SerializedTaskDispatcher* GetSerializedTaskDispatcher() {
return mSerializedTaskDispatcher;
void TriggerCalculation();
void DumpOccludingWindows(HWND aHWnd);
friend class ::WinWindowOcclusionTrackerTest;
friend class ::WinWindowOcclusionTrackerInteractiveTest;
explicit WinWindowOcclusionTracker(base::Thread* aThread);
virtual ~WinWindowOcclusionTracker();
// This class computes the occlusion state of the tracked windows.
// It runs on a separate thread, and notifies the main thread of
// the occlusion state of the tracked windows.
class WindowOcclusionCalculator {
// Creates WindowOcclusionCalculator instance.
static void CreateInstance();
// Clear WindowOcclusionCalculator instance.
static void ClearInstance();
// Returns existing WindowOcclusionCalculator instance.
static WindowOcclusionCalculator* GetInstance() { return sCalculator; }
void Initialize();
void Shutdown(layers::SynchronousTask* aTask);
void EnableOcclusionTrackingForWindow(HWND hwnd);
void DisableOcclusionTrackingForWindow(HWND hwnd);
// If a window becomes visible, makes sure event hooks are registered.
void HandleVisibilityChanged(bool aVisible);
void HandleTriggerCalculation();
// Registers event hooks, if not registered.
void MaybeRegisterEventHooks();
// This is the callback registered to get notified of various Windows
// events, like window moving/resizing.
static void CALLBACK EventHookCallback(HWINEVENTHOOK aWinEventHook,
DWORD aEvent, HWND aHwnd,
LONG aIdObject, LONG aIdChild,
DWORD aEventThread,
DWORD aMsEventTime);
// EnumWindows callback used to iterate over all hwnds to determine
// occlusion status of all tracked root windows. Also builds up
// |current_pids_with_visible_windows_| and registers event hooks for newly
// discovered processes with visible hwnds.
ComputeNativeWindowOcclusionStatusCallback(HWND hwnd, LPARAM lParam);
// EnumWindows callback used to update the list of process ids with
// visible hwnds, |pids_for_location_change_hook_|.
static BOOL CALLBACK UpdateVisibleWindowProcessIdsCallback(HWND aHwnd,
LPARAM aLParam);
// Determines which processes owning visible application windows to set the
// EVENT_OBJECT_LOCATIONCHANGE event hook for and stores the pids in
// |pids_for_location_change_hook_|.
void UpdateVisibleWindowProcessIds();
// Computes the native window occlusion status for all tracked root gecko
// windows in |root_window_hwnds_occlusion_state_| and notifies them if
// their occlusion status has changed.
void ComputeNativeWindowOcclusionStatus();
// Schedules an occlusion calculation , if one isn't already scheduled.
void ScheduleOcclusionCalculationIfNeeded();
// Registers a global event hook (not per process) for the events in the
// range from |event_min| to |event_max|, inclusive.
void RegisterGlobalEventHook(DWORD aEventMin, DWORD aEventMax);
// Registers the EVENT_OBJECT_LOCATIONCHANGE event hook for the process with
// passed id. The process has one or more visible, opaque windows.
void RegisterEventHookForProcess(DWORD aPid);
// Registers/Unregisters the event hooks necessary for occlusion tracking
// via calls to RegisterEventHook. These event hooks are disabled when all
// tracked windows are minimized.
void RegisterEventHooks();
void UnregisterEventHooks();
// EnumWindows callback for occlusion calculation. Returns true to
// continue enumeration, false otherwise. Currently, always returns
// true because this function also updates currentPidsWithVisibleWindows,
// and needs to see all HWNDs.
bool ProcessComputeNativeWindowOcclusionStatusCallback(
HWND aHwnd, std::unordered_set<DWORD>* aCurrentPidsWithVisibleWindows);
// Processes events sent to OcclusionEventHookCallback.
// It generally triggers scheduling of the occlusion calculation, but
// ignores certain events in order to not calculate occlusion more than
// necessary.
void ProcessEventHookCallback(HWINEVENTHOOK aWinEventHook, DWORD aEvent,
HWND aHwnd, LONG aIdObject, LONG aIdChild);
// EnumWindows callback for determining which processes to set the
// EVENT_OBJECT_LOCATIONCHANGE event hook for. We set that event hook for
// processes hosting fully visible, opaque windows.
void ProcessUpdateVisibleWindowProcessIdsCallback(HWND aHwnd);
// Returns true if the window is visible, fully opaque, and on the current
// virtual desktop, false otherwise.
bool WindowCanOccludeOtherWindowsOnCurrentVirtualDesktop(
HWND aHwnd, LayoutDeviceIntRect* aWindowRect);
// Returns true if aHwnd is definitely on the current virtual desktop,
// false if it's definitely not on the current virtual desktop, and Nothing
// if we we can't tell for sure.
Maybe<bool> IsWindowOnCurrentVirtualDesktop(HWND aHwnd);
static StaticRefPtr<WindowOcclusionCalculator> sCalculator;
// Map of root app window hwnds and their occlusion state. This contains
// both visible and hidden windows.
// It is accessed from WinWindowOcclusionTracker::UpdateOcclusionState()
// without using mutex. The access is safe by using
// SerializedTaskDispatcher.
std::unordered_map<HWND, OcclusionState> mRootWindowHwndsOcclusionState;
// Values returned by SetWinEventHook are stored so that hooks can be
// unregistered when necessary.
std::vector<HWINEVENTHOOK> mGlobalEventHooks;
// Map from process id to EVENT_OBJECT_LOCATIONCHANGE event hook.
std::unordered_map<DWORD, HWINEVENTHOOK> mProcessEventHooks;
// Pids of processes for which the EVENT_OBJECT_LOCATIONCHANGE event hook is
// set.
std::unordered_set<DWORD> mPidsForLocationChangeHook;
// Used as a timer to delay occlusion update.
RefPtr<CancelableRunnable> mOcclusionUpdateRunnable;
// Used to determine if a window is occluded. As we iterate through the
// hwnds in z-order, we subtract each opaque window's rect from
// mUnoccludedDesktopRegion. When we get to a root window, we subtract
// it from mUnoccludedDesktopRegion, and if mUnoccludedDesktopRegion
// doesn't change, the root window was already occluded.
LayoutDeviceIntRegion mUnoccludedDesktopRegion;
// Keeps track of how many root windows we need to compute the occlusion
// state of in a call to ComputeNativeWindowOcclusionStatus. Once we've
// determined the state of all root windows, we can stop subtracting
// windows from mUnoccludedDesktopRegion;.
int mNumRootWindowsWithUnknownOcclusionState;
// This is true if the task bar thumbnails or the alt tab thumbnails are
// showing.
bool mShowingThumbnails = false;
// Used to keep track of the window that's currently moving. That window
// is ignored for calculation occlusion so that tab dragging won't
// ignore windows occluded by the dragged window.
HWND mMovingWindow = 0;
// Only used on Win10+.
RefPtr<IVirtualDesktopManager> mVirtualDesktopManager;
// Used to serialize tasks related to mRootWindowHwndsOcclusionState.
RefPtr<SerializedTaskDispatcher> mSerializedTaskDispatcher;
friend class OcclusionUpdateRunnable;
static BOOL CALLBACK DumpOccludingWindowsCallback(HWND aHWnd, LPARAM aLParam);
// Returns true if we are interested in |hwnd| for purposes of occlusion
// calculation. We are interested in |hwnd| if it is a window that is
// visible, opaque, bounded, and not a popup or floating window. If we are
// interested in |hwnd|, stores the window rectangle in |window_rect|.
static bool IsWindowVisibleAndFullyOpaque(HWND aHwnd,
LayoutDeviceIntRect* aWindowRect);
void Destroy();
static void CallUpdateOcclusionState(
std::unordered_map<HWND, OcclusionState>* aMap, bool aShowAllWindows);
// Updates root windows occclusion state. If aShowAllWindows is true,
// all non-hidden windows will be marked visible. This is used to force
// rendering of thumbnails.
void UpdateOcclusionState(std::unordered_map<HWND, OcclusionState>* aMap,
bool aShowAllWindows);
// This is called with session changed notifications. If the screen is locked
// by the current session, it marks app windows as occluded.
void OnSessionChange(WPARAM aStatusCode,
Maybe<bool> aIsCurrentSession) override;
// This is called when the display is put to sleep. If the display is sleeping
// it marks app windows as occluded.
void OnDisplayStateChanged(bool aDisplayOn) override;
// Marks all root windows as either occluded, or if hwnd IsIconic, hidden.
void MarkNonIconicWindowsOccluded();
static StaticRefPtr<WinWindowOcclusionTracker> sTracker;
// "WinWindowOcclusionCalc" thread.
base::Thread* const mThread;
// Map of HWND to widget. Maintained on main thread, and used to send
// occlusion state notifications to Windows from
// mRootWindowHwndsOcclusionState.
std::unordered_map<HWND, nsWeakPtr> mHwndRootWindowMap;
// This is set by UpdateOcclusionState(). It is currently only used by tests.
int mNumVisibleRootWindows = 0;
// If the screen is locked, windows are considered occluded.
bool mScreenLocked = false;
// If the display is off, windows are considered occluded.
bool mDisplayOn = true;
RefPtr<DisplayStatusObserver> mDisplayStatusObserver;
RefPtr<SessionChangeObserver> mSessionChangeObserver;
// Used to serialize tasks related to mRootWindowHwndsOcclusionState.
RefPtr<SerializedTaskDispatcher> mSerializedTaskDispatcher;
friend class OcclusionUpdateRunnable;
friend class UpdateOcclusionStateRunnable;
} // namespace widget
} // namespace mozilla
#endif // widget_windows_WinWindowOcclusionTracker_h